<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
    <div id="root">
        姓:<input type="text" v-model="firstName"> <br />
        名:<input type="text" v-model="lastName"> <br />
        全名:<span>{{fullName}}</span>
        全名:<span>{{fullName}}</span>
        全名:<span>{{fullName}}</span>
    </div>

    <script type="text/javascript">
        const vm = new Vue({
            el: '#root',
            data: {
                firstName: '张',
                lastName: '三'
            },
            methods: {

            },
            computed: {
                fullName() {
                    console.log(this);
                    return this.firstName + '-' + this.lastName;
                }
            }
        })
    </script>

</body>

</html>